export {};
const [s1, s2]: string[] = require("fs").readFileSync(0).toString().trim().split("\n");
const [l1, l2]: number[] = [s1.length, s2.length];

let dp: number[][] = Array.from({length: l1+1}, () => new Array(l2+1).fill(0));

for(let i=1; i<=l1; i++) {
    let c1: string = s1[i-1];

    for(let j=1; j<=l2; j++) {
        let c2: string = s2[j-1];
        if(c1 === c2) dp[i][j] = dp[i-1][j-1] + 1;
        else dp[i][j] = Math.max(dp[i-1][j], dp[i][j-1]);
    }
}

console.log(dp[l1][l2]);

if(dp[l1][l2] !== 0) {
    let [p1, p2]: number[] = [l1, l2];
    let result: string[] = [];

    while(!(p1===0 || p2===0)) {
        const [c1, c2]: string[] = [s1[p1-1], s2[p2-1]];

        if(dp[p1][p2] === dp[p1][p2-1]) p2--;
        else if(dp[p1][p2] === dp[p1-1][p2]) p1--;
        else {
            result.push(c1);
            p1--; p2--;
        }
    }

    console.log(result.reverse().join(""));
}